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Gondwana, Ed. 3 Internet-Draft Fastmail 4 Updates: 5228 (if approved) 8 February 2021 5 Intended status: Standards Track 6 Expires: 12 August 2021 8 Sieve Email Filtering: delivery by mailboxid 9 draft-ietf-extra-sieve-mailboxid-07 11 Abstract 13 The OBJECTID capability of the IMAP protocol (RFC8474) allows clients 14 to identify mailboxes by a unique identifier which survives rename. 16 This document extends the Sieve mail filtering language (RFC5228) to 17 allow using that same unique identifier as a target for fileinto 18 rules, and for testing the existance of mailboxes. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on 12 August 2021. 37 Copyright Notice 39 Copyright (c) 2021 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 44 license-info) in effect on the date of publication of this document. 45 Please review these documents carefully, as they describe your rights 46 and restrictions with respect to this document. Code Components 47 extracted from this document must include Simplified BSD License text 48 as described in Section 4.e of the Trust Legal Provisions and are 49 provided without warranty as described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions Used In This Document . . . . . . . . . . . . . . 3 55 3. Sieve capability string . . . . . . . . . . . . . . . . . . . 3 56 4. Argument ":mailboxid" to Command "fileinto" . . . . . . . . . 3 57 4.1. Interaction with "mailbox" extension . . . . . . . . . . 4 58 4.2. Interaction with "specialuse" extension . . . . . . . . . 4 59 5. Interaction with "fcc" extension . . . . . . . . . . . . . . 5 60 6. Test "mailboxidexists" . . . . . . . . . . . . . . . . . . . 5 61 7. Interaction with variables extension . . . . . . . . . . . . 6 62 8. Security considerations . . . . . . . . . . . . . . . . . . . 6 63 9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6 64 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 65 11. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 11.1. draft-ietf-sieve-mailboxid-07 . . . . . . . . . . . . . 7 67 11.2. draft-ietf-sieve-mailboxid-06 . . . . . . . . . . . . . 7 68 11.3. draft-ietf-sieve-mailboxid-05 . . . . . . . . . . . . . 7 69 11.4. draft-ietf-sieve-mailboxid-04 . . . . . . . . . . . . . 7 70 11.5. draft-ietf-sieve-mailboxid-03 . . . . . . . . . . . . . 7 71 11.6. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 7 72 11.7. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 8 73 11.8. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8 74 11.9. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 8 75 11.10. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 8 76 11.11. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 8 77 12. Normative References . . . . . . . . . . . . . . . . . . . . 8 78 13. Informative References . . . . . . . . . . . . . . . . . . . 9 79 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 81 1. Introduction 83 [RFC5228] Sieve rules are sometimes created using graphical 84 interfaces which allow users to select the mailbox to be used as a 85 target for a rule. 87 If that mailbox is renamed, the client may also update its internal 88 representation of the rule and update the sieve script to match, 89 however this is a multi-step process and subject to partial failures. 90 Also, if the folder is renamed by a different mechanism (e.g. another 91 IMAP client) the rules will get out of sync. 93 By telling "fileinto" to reference the immutable mailboxid specified 94 by [RFC8474], using the extension specified herein, sieve rules can 95 continue to target the same mailbox even if it gets renamed. 97 2. Conventions Used In This Document 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 3. Sieve capability string 107 Scripts which use the following extensions MUST explicitly require 108 the capability "mailboxid". 110 Example: 112 require "mailboxid"; 114 4. Argument ":mailboxid" to Command "fileinto" 116 Normally, the "fileinto" command delivers the message in the mailbox 117 specified using its positional mailbox argument. However, if the 118 optional ":mailboxid" argument is also specified, the "fileinto" 119 command first checks whether a mailbox exists in the user's personal 120 namespace [RFC2342] with the specified [RFC8474] MAILBOXID. 122 If a matching mailbox is found, that mailbox is used for delivery. 124 If there is no such mailbox, the "fileinto" action proceeds as it 125 would without the ":mailboxid" argument. 127 The tagged argument ":mailboxid" to fileinto consumes one additional 128 token, a string with the objectid of the mailbox to file into. 130 Example: 132 require "fileinto"; 133 require "mailboxid"; 135 if header :contains ["from"] "coyote" { 136 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 137 "INBOX.harassment"; 138 } 140 4.1. Interaction with "mailbox" extension 142 For servers which also support the [RFC5490] mailbox extension, if 143 both the ":create" and ":mailboxid" arguments are provided to a 144 "fileinto" command and no matching mailbox is found, then a new 145 mailbox will be created. 147 This new mailbox will have the name specified by the positional 148 mailbox argument ([RFC5228] section 4.1), however it will get a 149 different mailboxid (chosen by the server) rather than the one 150 specified by the ":mailboxid" argument to fileinto. 152 Example: 154 require "fileinto"; 155 require "mailboxid"; 156 require "mailbox"; 158 fileinto :mailboxid "Fnosuch" 159 :create 160 "INBOX.no-such-folder"; 161 # creates INBOX.no-such-folder, but it doesn't 162 # get the "Fnosuch" mailboxid. 164 4.2. Interaction with "specialuse" extension 166 For servers which also support [RFC8579] delivery to special-use 167 mailboxes, it is an error to specify both ":mailboxid" and 168 ":specialuse" in the same fileinto command. 170 Advanced filtering based on both special-use and mailboxid can be 171 built with explicit "specialuse_exists" and "mailboxidexists" tests. 173 Note to developers of sieve generation tools: it is advisable to use 174 special-use rather than mailboxid when creating rules that are based 175 on a special-use purpose (e.g. delivery directly to the Junk folder 176 based on a header that was added by a scanning agent earlier in the 177 mailflow). 179 5. Interaction with "fcc" extension 181 This document extends the definition of the ":fcc" argument defined 182 in [RFC8580] so that it can optionally be used with the ":mailboxid" 183 argument. 185 If the optional ":mailboxid" argument is specified with ":fcc", it 186 instructs the Sieve interpreter to check whether a mailbox exists 187 with the specific mailboxid. If such a mailbox exists, the generated 188 message is filed into that mailbox. Otherwise, the generated message 189 is filed into the ":fcc" target mailbox. 191 Example: 193 require ["enotify", "fcc", "mailboxid"]; 194 notify :fcc "INBOX.Sent" 195 :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 196 :message "You got mail!" 197 "mailto:ken@example.com"; 199 6. Test "mailboxidexists" 201 The "mailboxidexists" test is true if all mailboxes listed in the 202 "mailboxids" argument exist in the mailstore, and each allows the 203 user in whose context the Sieve script runs to "deliver" messages 204 into it. When the mailstore is an IMAP server, "delivery" of 205 messages is possible if: 207 a) the READ-WRITE response code is present for the mailbox (see 208 Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL) 209 [RFC4314] is not supported by the server, or 211 b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of 212 [RFC4314]). 214 Note that a successful "mailboxidexists" test for a mailbox doesn't 215 necessarily mean that a "fileinto :mailboxid" action on this mailbox 216 would succeed. For example, the "fileinto" action might put user 217 over quota. The "mailboxidexists" test only verifies existence of 218 the mailbox and whether the user in whose context the Sieve script 219 runs has permissions to execute "fileinto" on it. 221 Example: 223 require "fileinto"; 224 require "mailboxid"; 226 if header :contains ["from"] "coyote" { 227 if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" { 228 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 229 "INBOX.name.will.not.be.used"; 230 } else { 231 fileinto "INBOX.harassment"; 232 } 233 } 235 Note to implementers: this test behaves identically to the 236 "mailboxexists" test defined in [RFC5490] but operates on mailboxids 237 rather than mailbox names. 239 7. Interaction with variables extension 241 There is no special interaction defined, however as an objectid is a 242 string in this document, objectid values can contain variable 243 expansions if [RFC5229] is enabled. 245 8. Security considerations 247 Because mailboxid is always generated by the server, implementations 248 MUST NOT allow sieve to make an endrun around this protection by 249 creating mailboxes with the specified ID by using ":create" and 250 ":mailboxid" in a fileinto rule for a non-existant mailbox. 252 Implementers are referred to the security considerations sections of 253 [RFC5228] and [RFC8474]. 255 9. IANA considerations 257 IANA are requested to add a capability to the sieve-extensions 258 registry: 260 To: iana@iana.org 261 Subject: Registration of new Sieve extension 263 Capability name: mailboxid 264 Description: adds a test for checking mailbox existence by objectid, 265 and new optional arguments to fileinto and :fcc which 266 allow selecting the destination mailbox by objectid. 267 RFC number: this RFC 268 Contact address: The EXTRA discussion list 270 10. Acknowledgements 272 This document borrows heavily from [RFC5490] for the matching 273 mailboxexists test, and from [RFC8579] for an example of modifying 274 the fileinto command. 276 Thanks to Ned Freed and Ken Murchison and Alexey Melnikov for 277 feedback on the EXTRA mailing list. 279 11. Changes 281 (EDITOR: remove this section before publication) 283 11.1. draft-ietf-sieve-mailboxid-07 285 * Martin Duke review - remove formal section 287 * Martin Duke review - wording for section 4.1 (interaction with 288 :create) 290 * Ken Murchison review - fixed :special-use to :specialuse per 291 RFC8579 293 11.2. draft-ietf-sieve-mailboxid-06 295 * GENART review - fixed example to not be semantically pointless 297 * GENART review - fixed !@ to @! in RFC reference mmark syntax 299 11.3. draft-ietf-sieve-mailboxid-05 301 * disallow :mailboxid and :special-use in the same fileinto action. 303 11.4. draft-ietf-sieve-mailboxid-04 305 * made RFC5490 and RFC8579 normative 307 * clarified wording based on AD feedback from Barry 309 11.5. draft-ietf-sieve-mailboxid-03 311 * Fixed ABNF syntax error 313 11.6. draft-ietf-sieve-mailboxid-02 315 * removed bogus : from "mailboxidexists" test title 316 * moved FCC to its own top-level section since it is not used with 317 the fileinto command. 319 11.7. draft-ietf-sieve-mailboxid-01 321 * fixed idnits - RFC5228 not mentioned in the abstract 323 * fixed other I-D references I had missed, oops 325 11.8. draft-ietf-sieve-mailboxid-00 327 * Adopted into working group per adoption call on list 329 * Updated references to old drafts which have since been published. 331 * Fixed some typoes and simplified some language. 333 * Removed stray leading colon on mailboxexists (thanks Alexey) 335 * Added :fcc to the IANA registration description (thanks Alexey) 337 * Mentioned that variables can be expanded (thanks Alexey) 339 11.9. draft-gondwana-sieve-mailboxid-02 341 * Update document date by a couple of years! Ooops, it got 342 forgotten after a WGLC which got not dissent. 344 * Create xml2rfc v3 output. 346 11.10. draft-gondwana-sieve-mailboxid-01 348 * Switch to :mailboxid tagged parameter value with fallback mailbox 349 name. 351 * Document interaction with "mailbox". 353 * Document interaction with "special-use". 355 * Document interaction with "fcc". 357 * Document security considerations around :mailboxid and :create. 359 11.11. draft-gondwana-sieve-mailboxid-00 361 * Initial version. 363 12. Normative References 365 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email 366 Filtering Language", RFC 5228, DOI 10.17487/RFC5228, 367 January 2008, . 369 [RFC8474] Gondwana, B., Ed., "IMAP Extension for Object 370 Identifiers", RFC 8474, DOI 10.17487/RFC8474, September 371 2018, . 373 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 374 Requirement Levels", BCP 14, RFC 2119, 375 DOI 10.17487/RFC2119, March 1997, 376 . 378 [RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342, 379 DOI 10.17487/RFC2342, May 1998, 380 . 382 [RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File 383 Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May 384 2019, . 386 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 387 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 388 May 2017, . 390 13. Informative References 392 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 393 RFC 5229, DOI 10.17487/RFC5229, January 2008, 394 . 396 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language -- 397 Extensions for Checking Mailbox Status and Accessing 398 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March 399 2009, . 401 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special- 402 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019, 403 . 405 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 406 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 407 . 409 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 410 RFC 4314, DOI 10.17487/RFC4314, December 2005, 411 . 413 Author's Address 415 Bron Gondwana (editor) 416 Fastmail 417 Level 2, 114 William St 418 Melbourne VIC 3000 419 Australia 421 Email: brong@fastmailteam.com 422 URI: https://www.fastmail.com